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USRSA String Test — February 2002

PACIFIC Natural Gut Strings have received the highest ratings in a recent USRSA test, the results of which appeared in the official USRSA publication, Racquet Tech (February 2002, page 4). This unbiased test, performed by Racquet Tech managing editor Crawford Lindsey with the help of USRSA technical advisor Professor Rod Cross, compared natural gut and synthetic strings head to head. The following is a summary of this report:

Test method:

  • All strings (12.6 inches) were tensioned to 62 lbs. (28.1 kg) and allowed to sit for 1000 seconds (approximately 17 minutes).
  • Each string was hit ten times with a force equivalent to that of a 120 mph (93 kph) serve. The total tension loss was a combination of the loss due to relaxation over time, and loss due to impact.
  • To test stiffness and elasticity, force was applied until each string deflected 1 inch (2.5 cm), and the amount of force noted.


  • PACIFIC PrimeGut is the softest of all strings tested, natural or synthetic.
  • 16-gauge PACIFIC PrimeGut is 4% softer that Babolat’s 17-gauge VS (96 pounds per inch of deflection versus 100 pounds). It’s an amazing 11% softer than Babolat 16-gauge VS (96 pounds versus 108 pounds).
  • PACIFIC Classic shows the least tension loss of all strings tested, natural or synthetic.
  • PACIFIC Classic is 9% better in tension retention than the industry standard, Babolat VS (6.8 pounds of tension loss versus 7.5 pounds).

The PACIFIC advantage:

  • Lower tension loss = longer performance life.
  • Lower deflection resistance = better playability (ball feel and control) and liveliness, with superior arm comfort.

What would an 4% (or 11%) improvement in playability, and a 9% gain in consistency and string life, do for your game? Use our special introductory offer to find out.

Company String Material Stiffness
Loss (lb)
PACIFIC PrimeGut 16 Gut 96 7.0
Babolat VS Power 17 Gut 100 7.9
PACIFIC Classic 16 Gut 104 6.8
Gamma Natural Gut 16 Gut 107 7.1
Bow Brand Natural Gut 16 Gut 108 7.2
Babolat VS Power 16 Gut 108 7.5
Unique Tourna Gut 17 Gut 113 7.1
Unique Tourna Gut 16 Gut 128 8.5

Gut tension loss vs stiffness

Installation Report

From: Greg Raven
Sent: Tuesday, June 05, 2002 9:55 AM
Subject: Pacific natural gut string evaluation

Here’s my report on Pacific natural gut string. This being my first time to string a racquet with natural gut, I will cover stringing issues that others may consider basic, in order to memorialize them.

The String:

The string was smooth and clear, so much so that it seemed almost to be polyester until examined closely. It was designated as a 16-gauge string. It measured 1.29 mm in diameter, which confirmed this. Measurements were taken at various points along the string, and consistency was very good from end to end. String length was more than enough for one of my matched 93 sq. inch Head i.Prestige racquets (20' mains x 16.5' crosses). I did not remeasure the string diameter after installation.

Installation — May 5, 2002:

The oversize coil unwound easily, and I found no flaws or even visual blemishes anywhere on the string. Minor snarls were easily cleared by gently shaking. Both ends were cut blunt.

Before stringing, I prepared the racquet by waxing a piece of 16-gauge synthetic string and “flossing” each grommet hole, to smooth any ridges and distribute a bit of the wax to serve as a lubricant during stringing. I also installed Teflon tubing in both 7T grommet holes to ensure that the damage at these grommet holes from tie-off knots would not cut the string.

My stringing machine is an “MS-700,” which is actually the drop weight “Czech Tension” sold in the U.S. by Machine Shop Stringers in Bakersfield. It is far from the best stringing machine around, but it is capable of consistent results. I set the clamps tight enough to prevent string slippage when pulling the first main (rather than backing up the first clamp with a flying clamp), so it is possible that I over-clamped the string. However, while the natural gut did reveal some dimpling from the clamps, I was able to pull tension without breaking the string, so I am assuming that my clamping technique did not egregiously damage the string.

The range of tension on this frame is 48-58 pounds. I strung the Pacific natural gut at 57 pounds, which is the same tension I have been using for synthetics.

The mains strung up better than any other string I've ever used, whether from the construction and smoothness of the string, the pre-waxing, or both: the tension was unbelievably even across all mains. I've never seen this with any of the several synthetic I've strung. On tensioning, the string turns opaque.

Stringing the crosses was more difficult for me. Weaving seemed more difficult, and after weaving, pulling the string through the mains felt “sticky.” I therefore waxed the mains over the face of the racquet, which helped a great deal to reduce the perceived “stickiness."

Because natural gut does not have the same stiffness and internal coherence of a synthetic, the leading 12 inches (or so) exhibited a lot of wear by the time I finished the crosses. No doubt, a better stringer would have less trouble in this area, and much of this portion of the string was cut off after tying off, so I just had to be careful when pulling through the weave on that section of string. (I think I can reduce the amount of thrashing of the last few crosses by changing how I pull the string through, I think I was elevating the string on both ends [which is fine, with synthetic!], but which increases the stress on the string.)

I found it easy to straighten the crosses as I worked. Synthetics seem to develop a mind of their own about where they will or will not go, but the Pacific natural gut stayed put, which I found very nice.

I had no trouble with kinking, perhaps because I kept a close eye on my loops.

The pointed end that I originally cut on the string was wonderfully sharp, and lasted until the next-to-the-last hole, which was blocked. I then cut about an inch off the end, and finished the last two holes (both of them, blocked) with no problem. I expected much more fraying, and have in fact experienced far greater fraying with some synthetics.

I also felt I was struggling with the tie-off knots, as the natural gut bends completely unlike synthetic. I was, however, able to get firm knots without resorting to pliers, and I'm happy with the end result.

The installed string has interesting color variations throughout the string-bed, which, while different than most synthetics, gives a pleasing “organic” appearance.

All in all, it took longer to string natural gut than synthetic, but I anticipated that, and the finished string job was worth the effort.

Initial Play Testing:

Compared to the relatively highly-rated synthetic that I normally use, Pacific natural gut is definitely softer. Hard serves with the synthetic sound as if the ball is smacking a concrete wall. Hard serves with the natural gut have an almost gentle impact, as if hitting the ball with a trampoline, but with excellent control. Also, despite the apparent smoothness of the string when new, I was able to get better spin than with the rougher synthetic I've been using. Touch and control on ground strokes were far better than with the synthetic, which is to be expected.

Pacific natural gut seemed to have about the same power as the synthetic I've been using, so the adjustment period should be relatively short.

The first time I played with Pacific natural gut (May 5), I hit about first serves for about 1.5 hours, about second serves for about .5 hours, and about .5 hours of volleys and groundstrokes. Afterwards, I felt no sensitivity in my wrist, elbow, or shoulder.

Further Play Testing:

In subsequent playing, I hit and played out points for about two hours on several days (May 7, 9, 11, 14, 16, 18, 21, 23, 25, 28, 30, June 1), hit against a backboard for about an hour apiece on May 9 and 26, and hit serves for about two hours on other days (May 12, 19, June 2). Taking into consideration that when hitting serves and hitting against the backboard, I take almost no breaks (aka “change-overs"), the strings have hit many more balls than they ever would have during game play of equal duration.

On May 12 alone, for instance, I hit close to 300 serves, and on May 9 after warming up with some groundstrokes and volleys, I hit 150 forehands and 150 backhands.As noted in the first part of this evaluation, the Pacific natural gut played softer than the relatively soft synthetic I've been using. With some exceptions, it seems to be about the same power level (for the same string tension). The main differences are that the natural gut has more “feel” and it is much easier on my arm than the synthetic.

On power shots (serves and big ground strokes, for example), the Pacific natural gut seems more responsive to the amount of energy you put into the shot. That is, with synthetic, there seem to be diminishing returns as racquet head speed goes up. With the natural gut, faster racquet head speed translates into a bigger shot to a much greater extent. Dialing back the power makes it easy to top-spin a high-angle shot.

On the other end of the scale, “touch” shots such as drop shots are much easier for me with the Pacific natural gut: with the synthetic I never felt as though I had complete control over touch shots, where with the natural gut, these heretofor difficult (for me) shots are predictable. My regular playing partner is very quick on his feet, so it was nice to see my drop shots actually landing out of range for him. In other words, the synthetic seems to have a smaller dynamic range than Pacific natural gut. The natural gut can hit harder, but it can also hit “softer,” which for me translates into predictable results based on the feedback I receive through the strings and racquet.

I wasn't expecting the 16-gauge string to allow much spin on the ball, but the Pacific natural gut gave me more spin than the 16-gauge synthetics I've been using. This really showed up on second serves and top-spin ground strokes.

Perhaps the most pleasant surprise was the improvement the string made to my high volleys. Because of my serve, I often get short, floating returns, which I should be able to come in on and volley away. With synthetic strings, I have a miserable percentage on this shot, as most of my volleys land just long. With the Pacific natural gut, these shots were landing well inside the line, with good “stick” on the ball.

The Pacific natural gut’s combination of spin and power level helped make my second serve tremendously effective. I can serve for placement, or put more juice on it and jump my second serve into the receiver’s body with great pace.

It took a couple of hundred serves to figure out where my first serve went, though. (It is normal when I make an equipment change that some aspect of my game needs re-evaluation.) I finally discovered that, to compensate for the differences between synthetic and Pacific natural gut, I could either place the toss for my first serve 3-4 inches farther into the court, or change my grip and open my stance a bit. Placing my toss farther out allowed me to hit some of the most impressive-looking first serves I've ever struck, with some balls hitting 6 feet up on the back fence, on the rise, after bouncing in the service box. However, my service percentage was not as dazzling, so I instead adopted a “pure” Continental grip and opened my stance, which allowed me to keep my existing service toss for both first and second serves, and preserved the effectiveness of my second serve.

On the forehand, I had been using a semi-Western grip, mostly because doing so virtually eliminated the elbow soreness I had been getting from using the Eastern grip with synthetic strings. With Pacific natural gut, I was able to go back to the Eastern grip, with no elbow soreness.

String Condition:

Even after hours of the extreme use to which I've put these strings, they seem to play the way they played when new. The center of the string bed is obviously rougher than the edges, which is to be expected. There seem to be some flaws showing up in the strings, but they are all in sections where I clamped the string, so this may have something to do with my stringing technique and/or equipment. There was no premature notching or fraying at the crosses. The strings stay put very well, and when they do move because of an off-center shot, they are easily straightened.


The synthetic I have been using “lasts” for five weeks (at roughly eight hours of play per week), although its playability drops off dramatically after three weeks (that is: two racquets strung at the same time with the same string to the same tension, switching off between the two racquets each time I play). Because I have strung only one racquet with Pacific natural gut, and am using that racquet exclusively, the observed longevity will be about half or less of the longevity I should get under normal conditions (switching off between two racquets, playing more game situations and fewer intensive hitting sessions). As recommended on the Pacific USA site, I have been treating the strings to a coating of carnauba wax after each hitting session.

At about 28 hours of play, small strands in the center of the string bed began to appear, although the strings seem to play the same as ever. With a synthetic, the string would be very dead by this point. At about 30 hours of play, larger strands had begun to separate from the string. I probably should have clipped them to prevent the ends from being caught between the ball and string bed and unravelling unnecessarily, but I decided to leave them attached to see what happened. (I also could have used string savers, but at least for the first test, chose not to.)

Finally, on June 2, at about 32 hours of play, one of the crosses snapped in the center of the string bed. When I cut the mains (remember this was a two-piece string job), they snapped — which tells me they still had some amount of tension in them. I've seen less residual tension in some synthetics that have fewer hours on them.

On switching to my back-up racquet, I was immediately struck by the superficial similarities between synthetic and natural gut — I felt that I would be able to do everything with the synthetic that I had been doing with the natural gut. However, the similarities were illusory: my ability to hit drop shots and high volleys had again disappeared, and other subtle differences became manifest on almost every point.

Overall Playing Impressions:

I see why players get “hooked” on natural gut strings. They seem to do everything well, and they feel great in the process. Even compared to premium, high-end strings such as Tecnifibre NRG SPL, which are supposed to play similarly to natural gut, the Pacific natural gut is clearly superior in playability and surprisingly, durability.

— Greg Raven